This invention relates to an improvement of tripod type constant velocity joints.
In a conventional tripod type constant velocity joint which generally has been used, it is known that said tripod type constant velocity joint receives axial forces, three times per one revolution in its rotation with a torque when operated in certain angle.
Due to fluctuation of the axial force by the extent of joint angle, transmitting torque, etc., particularly in a recent high powered vehicle, the fluctuation of said axial force is likely to become larger or increase. Further, in the cases that the occurence cycle of axial force corresponds to that of the proper frequency of a vehicle body, vehicle suspension and the like, and the axial force is strong enough to induce co-vibration of the vehicle, there is the convenient problem that a crew in a vehicle feesl uncomfortable lateral shaking.
To solve such an inconvenient problem, a proposal has been made in the U.S. patent application No. 06/750,590 by this applicant.
The constant velocity joint relating to this proposal as shown in FIG. 3 and FIG. 4 consists of U-shaped aligning means disposed between three raceways 1 in a housing H and three cylindrical rollers R in such way that said aligning means fitting into raceways 1 pinch the cylindrical rollers, each of which is mounted movably on a trunnion 2 provided on a shaft. The aligning member means U has, as its contact surface with a cylindrical surface r.sup.1 of the raceway 1, a continuous or discontinuous cylindrical surface r.sup.2, The aligning member means U is axially maintained within the housing H at one end by support tabs at the open end of the raceways 1 so that said aligning member means U is movable relatively in the raceway, and has a flat plane P on the inner side surface contacting with surface of the cylindrical roller R. The cylindrical roller R rolls on said flat plane P, to thus reduce the axial force. Further, in the drawing, 3 indicates a needle, and 4 indicates striker ring fixed to stop ring 5 which corresponds to element 15 of FIG. 28 of said 06/750,590 copending application.
However, since the aligning member means used here is formed from drawn steel material and heat treated to improve the durability, it has been unavoidable to have manufacturing errors or heat treating distortions caused in such processes and to have discontinuous or partial line contacts different from the ideally continuous line contacts between a cylindrical roller R and a plane P of the aligning member means U.
Accordingly, there remained an inconvenient problem that the axial force caused by a rolling friction resistance force of the cylindrical roller R between the cylindrical roller R and the aligning member means U and causing the shaking of a vehicle is not reduced sufficiently.
The following is the result of the cause analysis of the above operation:
Now, the drawing in FIG. 5 indicates mutual relations of sliding and rolling forces which occur in the state of contact or in the contact part the cylindrical roller R contacting the flat plane P in their exact dimensions.
Further in the invention, as explained later, since the purpose of this invention is to reduce the axial force by analyzing a friction resistance force in the rolling movement of the cylindrical roller R on the flat plane P, other forces are disregarded here.
In the drawing, O is the joint center, .theta. is a joint angle, OY.sup.1 is center line of a trunnion in the joint angle .theta., OY.sup.2 is the centerline of the trunnion in the case of joint angle zero only assumed on this drawing. A,B,C are three optional spots having each load on the contact part (line) OY.sup.1 of the cylindrical roller R contacting the plane P.
When the axis of cylindrical roller R moves to the direction from OY.sup.1 to OY.sup.2, B becomes a spot to show the pure rolling movement and A and C become highest in sliding movements and both A and C work in the opposite direction each other. fA, fB, fC are friction resistance forces which work on the cylindrical roller at said spots A, B and C. fA and fC occur due to a sliding movement, fB occurs due to a friction force between the cylindrical roller R and the trunnion 2, and friction etc. between the cylindrical roller and the striker ring 4, each works to the directions shown by each arrow mark. f.sup.1 and f.sup.0 are forces which occur at the center of the joint and affect the axial force, and f.sup.1 is a rolling friction resistance force which affects on the axial force caused by fB and it can be f1=fB, f.sup.0 is an counter force which occurs by fA and fC, and can be calculated as follows. That is, OB=lb and AC=L1 (almost same as the width of aligning member means) are given, suppose fA=fC is assumed in order to make a calculation easy, fo . fb=fA . l1 will be fo=l1/lb.times.fA. By this analysis, it can be seen that fo and f.sup.1 are in the opposite direction to one another and fA and fC caused by the sliding movement are effective in reducing the axial force.
However, since there are some manufacturing errors or heat treating distortions caused by heat treatment as explained previously, any sliding movement does not happen without contacts at spots A and C for the reason mentioned previously and due to only partial contact at B or in its vicinity only a rolling friction resistance force of the cylindrical roller occurred in the actual practice. Accordingly f.sup.1 remained there as an axial force and caused every kind of vibrations.